Seeing Red

My print column examines the controversy over red-light cameras, and the occasionally conflicting numbers about whether the hundreds of local laws are successful in reducing red-light running and the sometimes-dangerous crashes that can result.

Last week, the Insurance Institute for Highway Safety published findings that red-light-running violations had declined at intersections with the cameras in Arlington, Va. “The study is consistent with other studies” showing that the cameras make intersections safer, said Anne T. McCartt, co-author of the report and senior vice president for research at IIHS, which is funded by the insurance industry.

But other researchers question the use of violations as a measure of safety. “As soon as you hear them talk about violation rates, these people are trying to obfuscate the fact that accidents don’t go down,” said Declan O’Scanlon, a New Jersey state assemblyman and an opponent of the cameras.

“It is meaningless to study violations,” Barbara Langland Orban, an associate professor of health policy and management at the University of South Florida, wrote in an email. “Safety is measured in crashes, in particular injury crashes, and violations are not a proxy for injuries. Also, violations can be whatever number an agency chooses to report, which is called an ‘endogenous variable’ in research and not considered meaningful as the number can be manipulated. In contrast, injuries reflect the number of people who seek medical care, which cannot be manipulated by the reporting methods of jurisdictions.”

McCartt responded that the study is just the first step in planned research into the effect of Virginia cameras, which recently have been re-instituted after an earlier law authorizing their use expired. “It’s part of bigger research we’re going to do, looking at Virginia,” McCartt said. “It’s going to allow us to do very strong research design.”

The IIHS is one of the major producers of research in the field, which generally has found that the cameras are effective. Some camera critics question the IIHS’s motives, since its members can charge some motorists if they have been ticketed for running a red light. “It is financially to their benefit to have more camera tickets issued,” said James C. Walker, a board member of the National Motorists Association, a 10,000-member drivers organization in Waunakee, Wis., that opposes the cameras. “To me, they’re just not unbiased.”

Orban, co-author of severalpapers critical of IIHS research, also made this criticism. “We caution against using IIHS studies as evidence of camera effectiveness,” Orban said, adding, “They have a financial conflict of interest.”

McCartt responded that most states with cameras bar insurers from raising premiums because of camera-caught violations. She added that the organization has no bias and would publish results that aren’t supportive of the cameras. “Whatever we find, we put it out there,” McCartt said. She added, of the South Florida group that has criticized IIHS, “We have a difference of opinion about what constitutes a strong study.”

Some defend the institute. Justin McNaull, director of state relations for the national motorists organization American Automobile Association Inc., said “IIHS generally does good research.” McNaull added, of red-light cameras, “We’re supportive of them as one part of an approach to increase safety.”

Simon Washington, a civil-engineering professor at Queensland University of Technology in Brisbane, Australia, said of IIHS studies, “Generally they’re quite good.”

The institute also has hit back at some studies that don’t find gains, such as a study funded by the Virginia department of transportation in 2007 that found the increase in rear-end crashes wiped out gains from a decrease in other crashes, even after accounting for severity of crashes. The study considered an earlier implementation of the cameras than the more recent IIHS study, and included Arlington.

Richard Retting, now a consultant with Sam Schwartz Engineering in Fairfax, Va., was at the IIHS, and with colleagues he published a critique of the study. Today he calls the Virginia study “flawed.”

John S. Miller, principal research scientist at the research division of Virginia’s transportation department’s and co-author of the report, said he and his co-authors sent a private response to the IIHS in which they reported that after making the changes to their analysis suggested by the institute, they found the same result. “When we took every single one of their suggestions, it did not change the results of the study,” Miller said.

Retting said the “preponderance of evidence” shows cameras work. “We have in our field information that’s not 100% definitive, but it’s as good as it gets considering we’re not studying in laboratory conditions,” he said. He adds that the IIHS has a strong reputation from decades of work promoting safety. “There’s no logical reason why IIHS would focus on a countermeasure that doesn’t improve safety,” Retting said.

With this sort of controversy over the effectiveness of cameras, it can be difficult for local governments deciding whether they should use cameras as a tool to boost traffic safety. Some that have — including Philadelphia, Los Angeles, St. Petersburg, Fla., and New Jersey — then have found that, at least by certain ways of counting, overall crashes increase. Rear-end crashes — which tend to be common to begin with — often rise as drivers hit the brakes when they spot warnings of cameras.

To Retting, a raw count of crashes before and after the introduction of red-light cameras isn’t a good evaluation of their effectiveness. “Analysis requires more effort than just asking police what the numbers were,” he said. “In some ways it could be a waste of resources and provide misinformation unnecessarily.” He said that local governments should look to published, scientific research rather than make decisions based on their own raw numbers.

Statistical analysis that goes beyond raw crash counts can have a big effect on findings. The Virginia transportation department report found that, in raw terms, all crashes increased by 12% at red-light-camera intersections. But after conducting what’s called a Bayes empirical analysis, the finding was that the cameras were associated with a 29% increase in all crashes, and an 18% increase in injury-causing crashes.

A New Jersey transportation department report late last year showed that the same results can be interpreted in many different ways. Retting pointed out that at two intersections with cameras for two years, “right-angle crashes and overall crashes declined substantially.” He added that the positive effects of cameras may have been underestimated by the report because it used as controls intersections near the camera-equipped ones, and any effect on drivers may have spilled over to those intersections without cameras.

Joseph Dee, a spokesman for the New Jersey transportation department, also mentioned the two sites with positive results, but added, “You’d laugh at me if we said we have two locations” with good results for cameras. The overall results, counting the many more sites with less experience with the cameras, showed that incidence of most types of crashes increased. “We will monitor the data as time goes on and we certainly hope that the crashes decrease over time as motorists become more familiar with red-light-camera controlled intersections,” Dee said.

But O’Scanlon said the data are damning. He said that if he were irresponsible with the data, he would argue that the New Jersey results show that cameras make intersections more dangerous. He recognizes, though, that random statistical fluctuations could account for the finding, and instead makes the milder case that they are neutral or slightly negative. “You will not find me torturing the data to increase the drama of my argument,” said O’Scanlon, a Republican who represents a district in the northern Jersey shore. “I don’t play that game. I’m an honest guy.”

Los Angeles City Councilman Dennis P. Zine opposed his city’s cameras because of local data, and the cameras were phased out in 2011. Citing a study by local journalists that found crashes increased at most intersections, he said, “The investigative report demonstrated that the red-light cameras may have even led to an increase in accidents at some locations.” Zine added, “There was no proof that it positively impacted public safety and there were studies countering the intended enhanced safety measure.

Various figures in the research of, and debate over, red-light cameras offered tips for local governments deciding whether to implement them. “Study design is really important,” said Kimberly Eccles, a principal at Vanasse Hangen Brustlin Inc., an engineering consulting firm. She added, “My first advice would be, seek a third party,” such as, for a city, its state’s transportation department, to help it study the cameras’ effects.

The AAA’s McNaull said local governments have to gather local data, if only to convince local motorists of cameras’ benefits. “Unless you’re regularly communicating with the public, showing the benefit, the only way the public hears about them is when the public gets tickets,” McNaull said. “It’s certainly a challenge for policymakers.”

“Data indicate that red-light camera systems can be a very effective countermeasure to prevent red-light running, but the decision to use red-light cameras is a matter for local decision makers,” said a spokesman for the Federal Highway Administration.

David Banks, professor of statistical science at Duke University, said that researchers and governments shouldn’t be overly swayed by fatal crashes, which are rare, more subject to random fluctuation and can dwarf other incidents with their high severity and cost. “In the traffic community it is pretty standard practice to look at smaller accidents that are more common or precursor events, such as fender benders, or people turning without signals, rather than rely solely on very noisy, rare events,” Banks said. “I would not rush to use fatalities as a standard for estimating risk.”

Washington said the initial choice of intersections is crucial. “Surprisingly, there were a lot of jurisdictions that made decisions [about camera placement] largely driven by political decisions or responses to citizen requests, and those may not be intersections that yield the greatest benefits,” Washington said. An increase in rear-end crashes coupled with a decline in right-angle crashes is a tradeoff that “is almost always worth it,” Washington added. “It’s usually a tradeoff most professionals would be willing to make. But if you don’t have a lot of red-light running crashes [to begin with], the tradeoff might not be worth it.”

Washington co-authored a study for the Arizona Department of Transportation in 2005 that, typical of the confusing nature of red-light-camera research, found that the cameras had only minor positive safety benefits in Phoenix but major benefits safety in neighboring Scottsdale.

Washington added that there is an additional benefit not often touted by backers of the cameras: Both the revenue they raise, and the time they free up for police officers to enforce laws other than those barring red-light running, can go toward boosting safety. “Citizens often complain about seeing something as a revenue raiser,” Washington said. “But the reality is, if you’re funding other safety programs, and saving other lives in a network, it’s hard to argue it’s a bad outcome.”

Retting, a backer of the cameras, said that other measures could be more effective in some circumstances. “They’re not a panacea,” he said. “Traffic lights themselves are not a panacea. There are better ways to run intersections, particularly through the use of roundabouts.”

About The Numbers

The Wall Street Journal examines numbers in the news, business and politics. Some numbers are flat-out wrong or biased, while others are valid and help us make informed decisions. We tell the stories behind the stats in occasional updates on this blog.